mei: drop redundant krealloc and checks in irq read

The read callback is always prepared with MTU-sized buffer and the FW
can't send more than the MTU in one message.
Checking for buffer existence and krealloc to increase receive buffer
size are redundant and may be safely discarded.
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/interrupt.c

@@ -102,18 +102,17 @@ int mei_cl_irq_read_msg(struct mei_cl *cl,
 {
 	struct mei_device *dev = cl->dev;
 	struct mei_cl_cb *cb;
-	unsigned char *buffer = NULL;
 	size_t buf_sz;
 
 	cb = list_first_entry_or_null(&cl->rd_pending, struct mei_cl_cb, list);
 	if (!cb) {
 		if (!mei_cl_is_fixed_address(cl)) {
 			cl_err(dev, cl, "pending read cb not found\n");
-			goto out;
+			goto discard;
 		}
 		cb = mei_cl_alloc_cb(cl, mei_cl_mtu(cl), MEI_FOP_READ, cl->fp);
 		if (!cb)
-			goto out;
+			goto discard;
 		list_add_tail(&cb->list, &cl->rd_pending);
 	}
 
@@ -121,14 +120,7 @@ int mei_cl_irq_read_msg(struct mei_cl *cl,
 		cl_dbg(dev, cl, "not connected\n");
 		list_move_tail(&cb->list, &complete_list->list);
 		cb->status = -ENODEV;
-		goto out;
-	}
-
-	if (cb->buf.size == 0 || cb->buf.data == NULL) {
-		cl_err(dev, cl, "response buffer is not allocated.\n");
-		list_move_tail(&cb->list, &complete_list->list);
-		cb->status = -ENOMEM;
-		goto out;
+		goto discard;
 	}
 
 	buf_sz = mei_hdr->length + cb->buf_idx;
@@ -139,25 +131,19 @@ int mei_cl_irq_read_msg(struct mei_cl *cl,
 
 		list_move_tail(&cb->list, &complete_list->list);
 		cb->status = -EMSGSIZE;
-		goto out;
+		goto discard;
 	}
 
 	if (cb->buf.size < buf_sz) {
 		cl_dbg(dev, cl, "message overflow. size %zu len %d idx %zu\n",
 			cb->buf.size, mei_hdr->length, cb->buf_idx);
-		buffer = krealloc(cb->buf.data, buf_sz, GFP_KERNEL);
 
-		if (!buffer) {
-			cb->status = -ENOMEM;
 		list_move_tail(&cb->list, &complete_list->list);
-			goto out;
-		}
-		cb->buf.data = buffer;
-		cb->buf.size = buf_sz;
+		cb->status = -EMSGSIZE;
+		goto discard;
 	}
 
-	buffer = cb->buf.data + cb->buf_idx;
-	mei_read_slots(dev, buffer, mei_hdr->length);
+	mei_read_slots(dev, cb->buf.data + cb->buf_idx, mei_hdr->length);
 
 	cb->buf_idx += mei_hdr->length;
 
@@ -169,10 +155,10 @@ int mei_cl_irq_read_msg(struct mei_cl *cl,
 		pm_request_autosuspend(dev->dev);
 	}
 
-out:
-	if (!buffer)
-		mei_irq_discard_msg(dev, mei_hdr);
+	return 0;
 
+discard:
+	mei_irq_discard_msg(dev, mei_hdr);
 	return 0;
 }